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Hi Prajnyajit,
Regarding 1, there is no BQ25505EVM however there is a BQ25570EVM, which can be modified to fit the BQ25505. I recommend ordering an EVM to help debug your circuit.
Regarding 2, the BQ25505 is a boost converter so if you input 3V your output at VSTOR=VBAT must be greater than 3V. You set the output using the resistors at BAT_OV. You can use the spreadsheet at this link to help size the resistors. https://www.ti.com/lit/zip/sluc484
Regarding 3, see answer to questions 2.
Regards,
Jeff
Thanks Jeff, that will really help me this. Can you help me little more in this by answering the followings?
1. What is the use or function of an EVM of these PMICs?
Can't I use BQ25505 directly in my system with the proper circuits as mentioned in manual ? If yes, what possible difficulties I may face?
2. Can you say, what is the ratio of output voltage and input voltage in BQ25505.
3. BQ25505 has input voltage range of 0.6V-5.1V, so should I choose a PV cell whose open circuit voltage (Voc) ) must be within 5.1V or I can choose a PV cell whose Voc can be more than 5.1V like 6V or 6.5V so that the average output of PV cell will be in the range of 4V?
Again thank you sincerely for sharing the above tips with me.
Hi Prajnyajit,
Regarding 1, yes, you can install the IC directly on your PCB. The EVM makes prototyping (i.e. changing resistors to get the voltages your want) easier.
Regarding 2, you set the output voltage of at VSTOR=VBAT using the VBAT_OV resistors. From the power balance equation: efficiency= (VSTOR*ISTOR)/(VIN_DC*IN_DCavg), with VIN_DC fixed at MPP and IN_DCavg=avg of the peak inductor current pulses (see datasheet figure 18 for example), the higher VSTOR is set the lower ISTOR must be.
Regarding 3, your PV cell MPP=(80% of VOC) must be lower the your output voltage at VSTOR set by the VBAT_OV resistors because this is a boost charger (i.e. charger must boost up its input voltage).
Regards,
Jeff